1. Field of the Invention
The present invention relates no a projection exposure apparatus used in a lithography process in the manufacture of semiconductor elements, liquid crystal elements, and the like.
2. Related Background Art
A so-called step-and-repeat-type stepper is known as a conventional projection exposure apparatus. In this apparatus, the entire pattern of an original sheet (reticle) on which a circuit to be projected and exposed is drawn is sequentially projected and exposed onto a photosensitive substrate such as a wafer or a plate coated with a photosensitive agent for every shot through a projection exposure optical system (projection lens). This apparatus is excellent in resolving power and throughput.
In recent years, a scanning-type projection exposure apparatus has been proposed to achieve a higher throughput at a higher resolving power.
A scanning-type projection exposure apparatus is proposed in, e.g., Proc.SPIE 1088(1989) pp 424-433. In this apparatus, a reflecting reduction optical system having a circular arc image field is used to project and expose a pattern on a reticle onto a wafer.
Another scanning-type projection exposure apparatus uses a normal projection optical system (full-field-type projection optical system) having a circular image field to project and exposure a pattern on a reticle onto a wafer by a step-and-scan method. For example, Japanese Patent Laid Open No. 4-196513 proposes a method in which a rectangular (slit-like) image field whose long and short sides have different lengths is scanned. This proposed apparatus can ensure a higher resolving power while realizing a higher throughput by a wide exposure field. Therefore, this apparatus has received a great deal of attention as a promising exposure apparatus succeeding the above-described step-and-repeat-type exposure apparatus.